One of the many challenges in miniaturization of wireless communication devices is the lack of a sufficiently large ground plane for an antenna.
As described in US Publication No. 2008/0252536 A1 to Anguera et al., a conventional antenna set for a portable wireless communication device, such as a cell phone, includes an antenna element and a ground plane. The communication device includes a multi-layer printed circuit board (PCB), one of the layers of which serves as a ground plane for the antenna.
Design of an antenna set is done in conjunction with development of the communication device. Antenna design is based inter alia on form factor of the communication device, PCB layout, and location of different elements, especially metallic elements such as hinges, rails, cables, audio lines, LCD and battery. The antenna set is calibrated by performance testing that recursively tests modifications in the antenna with the hardware and the form factor of the communication device. The antenna set is performance tested in several scenarios, with different hand positionings of the phone and fingers covering the antenna.
In order for the antenna to perform well, in terms of its bandwidth, efficiency and gain, the ground plane must be sufficiently large relative to the wavelengths of the frequencies of operation of the antenna. But as the size of the communication device shrinks, the size of the ground plane is correspondingly reduced, yet the frequencies of operation of the antenna must remain substantially unchanged. As such, performance of the antenna degrades.